Wireless communication device, wireless communication terminal and wireless communication method

ABSTRACT

According to one embodiment, a wireless communication device includes: a memory configured to store a plurality of radiation pattern selection policies on an antenna capable of changing a radiation pattern; and processing circuitry configured to detect an interference signal of a first channel by analyzing a signal received via the antenna; and select the radiation pattern selection policy from among the plurality of radiation pattern selection policies based on the interference signal of the first channel and change the radiation pattern of the antenna in accordance with the selected radiation pattern selection policy.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2016-183282, filed on Sep. 20, 2016; theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate to a wireless communication device,a wireless communication terminal and a wireless communication method.

BACKGROUND

In a wireless LAN (Local Area Network), a CSMA/CA (Carrier SenseMultiple Access/Collision Avoidance) scheme is used. In the CSMA/CAscheme, the state of a wireless medium is checked by carrier sensing,and, when the state is idle, an access right is acquired to performframe transmission.

In a wireless LAN, there may be a case where an operating channel ischanged depending on a congestion condition of the operating channel,handover and the like. In this case, as an example of an operation of anaccess point, an operation of notifying the change of the operatingchannel to terminals by broadcasting a channel switching signal to theterminals is given. For example, in IEEE 802.11h, it is possible for theterminals to perform channel change without performing associationagain, by receiving the channel switching signal from the access point.

However, when a device which continues emitting a radio wave (aninterference signal), such as an analog video camera and an analogtelephone, exists near the access point, it is difficult for the accesspoint to acquire an access right. In this case, the access point cannottransmit a channel switching signal, or it takes a long time before theaccess point can transmit a channel switching signal. When the accesspoint compulsorily performs switching of the operating channel withouttransmitting a channel switching signal, each terminal is required toperform an association process with the access point again, and it takea time until communication becomes possible. Thus, existence of a devicewhich continues emitting an interference signal becomes an obstacle tocommunication of a wireless LAN system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a wireless communication device accordingto a first embodiment;

FIG. 2 is a block diagram of an interference detector according to thefirst embodiment;

FIG. 3 is a diagram showing an example of time-frequency data accordingto the first embodiment;

FIG. 4 is a diagram schematically showing an example of features and anexample of binary tree used to determine a device category of aninterference source by a classifier according to the first embodiment;

FIG. 5 is a flowchart of an operation by the wireless communicationdevice according to the first embodiment;

FIG. 6 is a flowchart continued from FIG. 5;

FIG. 7 is a diagram showing an example of a state in which interferenceis detected;

FIG. 8 is a diagram showing an example of changing a radiation patternand continuing communication through the same channel;

FIG. 9 is a diagram showing an example of changing the radiation patternand transmitting a channel switching signal through the same channel;

FIG. 10 is a diagram showing an example of a state in which the wirelesscommunication device and a part of terminals have switched the channel;

FIG. 11 is a diagram showing a state in which remaining terminals haveswitched the channel;

FIG. 12 is a flowchart of an operation according to a firstmodification;

FIG. 13 is a flowchart of an operation according to a secondmodification;

FIG. 14 is a functional block diagram of an access point or a terminalaccording to a second embodiment;

FIG. 15 is a diagram showing a whole configuration example of theterminal or a base station;

FIG. 16 is a diagram showing a hardware configuration example of awireless communication device mounted on the terminal or the basestation;

FIG. 17 is a perspective view of a wireless communication terminalaccording to the embodiment of the present invention;

FIG. 18 is a diagram showing a memory card according to the embodimentof the present invention; and

FIG. 19 is a diagram showing an example of frame exchange during acontention period.

DETAILED DESCRIPTION

According to one embodiment, a wireless communication device includes: amemory configured to store a plurality of radiation pattern selectionpolicies on an antenna capable of changing a radiation pattern; andprocessing circuitry configured to detect an interference signal of afirst channel by analyzing a signal received via the antenna; and selectthe radiation pattern selection policy from among the plurality ofradiation pattern selection policies based on the interference signal ofthe first channel and change the radiation pattern of the antenna inaccordance with the selected radiation pattern selection policy.

Embodiments of the present invention will be described below withreference to drawings. In the drawings, the same components will begiven the same reference numerals, and description thereof will beappropriately omitted.

First Embodiment

FIG. 1 is a block diagram showing an example of a wireless communicationdevice according to the present embodiment. A wireless communicationdevice 1 is provided with an interference detector 10, a variableantenna portion 11, a controller 12, a storage 14 and a communicator 15.The controller 12 is provided with an antenna switcher 16 and acommunication controller 17.

The wireless communication device 1 is, for example, an access point(hereinafter also referred to as a base station) constituting a wirelessLAN and is a device which transmits and receives frames to and from apartner wireless communication device using a wireless medium such as aradio wave. The partner wireless communication device is a wirelesscommunication terminal belonging to a network formed by the access point(BSS: Basic Service Set). Hereinafter, the wireless communicationterminal may be referred to as a terminal, a communication terminal oran STA (station). The access point (base station) has functions similarto those of a station except that the access point has a relay functionand the like and, therefore, is in one form of a wireless communicationterminal. In a case of mentioning a non-base station terminal, it refersto a station. In a case of merely mentioning a wireless communicationterminal (terminal), it may refer to not only a station but also anaccess point.

Though the wireless communication device 1 is assumed to be an accesspoint in the present embodiment, the wireless communication device 1 isnot limited to an access point. For example, the wireless communicationdevice 1 may be a terminal or may be a wireless communication deviceother than a wireless LAN communication device.

The wireless communication device other than a wireless LANcommunication device will be described. In a wireless LAN communicationdevice, an LBT (Listen before Talk) scheme is adopted. Specifically, aCSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) scheme isused. In the CSMA/CA scheme, the state of a wireless medium is checkedby carrier sensing, and, when the state is an idle state, a right ofaccess to the wireless medium is acquired to perform frame transmission.The wireless communication device according to the present embodimentmay be a wireless communication device other than a wireless LANcommunication device if the wireless communication device constitutes asystem using such an LBT scheme. As an example of a system using the LBTscheme other than a wireless LAN system, an LAA (Licensed AssistedAccess using LTE (Long Term Evolution)) system is given. The LAA is ascheme for performing LTE communication using a frequency band whichdoes not require license.

The variable antenna portion 11 is provided with one or more antennasfor transmitting and receiving radio waves. The variable antenna portion11 radiates a wireless frequency signal supplied from the communicator15 into space as a radio wave. Further, the variable antenna portion 11outputs a wireless frequency signal received from the space to theinterference detector 10 and the communicator 15.

Here, the variable antenna portion 11 has a plurality of radiationpatterns and can change its radiation patterns by switching antennasettings. The radiation pattern is also referred to as a beam pattern.Hereinafter, the patterns will be referred to as radiation patterns. Asexamples of the radiation pattern, an omnidirectional pattern, a patternhaving directivity in a particular direction and the like are given. Apattern obtained by arbitrarily combining (overlapping) the patterns isalso possible.

An example of a structure of an antenna capable of changing itsradiation pattern will be described. As an example, a configuration isgiven in which one antenna has a plurality of branches, and directivityof the antenna is controlled by controlling impedance or resistance ofeach branch. For example, when the antenna has four branches, aplurality of impedance setting patterns for the four branches areprepared, and the directivity of the antenna is controlled by switchingamong the setting patterns. An access point is provided with one or moresuch antennas. In a case of being provided with a plurality of suchantennas, a composite radiation pattern may be generated by combiningdirectivities of the antennas. Otherwise, as another configuration, aconfiguration is also possible in which an antenna is configured bysurrounding one antenna element with four metal plates so that a radiowave radiated from the antenna element are reflected by the metal platesand transmitted. In this case, the directivity of the antenna iscontrolled by adjusting an angle or position of each metal plate.Antenna structures other than those described here are also possible.

The antenna switcher 16 changes the radiation pattern of the variableantenna portion 11 by switching settings for the variable antennaportion 11. The antenna switcher 16 changes the radiation pattern inaccordance with an instruction from the communication controller 17.

The interference detector 10 detects interference signals of anoperating channel used by the wireless communication device 1 and otherchannels by analyzing a received signal from the variable antennaportion 11. When an interference signal is detected, a characteristic ofthe interference signal are grasped. For example, it is identifiedwhether interference with another communication device in the operatingchannel is interference with a high duty ratio. The operating channel isa channel being used for communication among a plurality of frequencychannels set for a frequency domain. The duty ratio is a rate of periodduring which signals with a level equal to or higher than a thresholdhave been received, among signals received within a predeterminedperiod. Details of the operation of the interference detector 10 will bedescribed later.

The communication controller 17 performs control related tocommunication of the wireless communication device 1, control of theradiation pattern of the variable antenna portion 11, channel switchingcontrol and the like.

The communication controller 17 performs communication protocolprocessing as the control related to communication. In the case of awireless LAN, the communication protocol processing includes MAC layerprocessing. Specifically, generation of a MAC frame, analysis of areceived MAC frame, processing based on an analysis result and the likeare included. Processing for an upper layer above the MAC layer (theTCP/IP layer, the UDP/IP layer or the like) may be included. When thekinds of the MAC frames are roughly classified, there are data frame,management frame and control frame, and any of the frames is possible.The data frame is a frame for transmitting data generated inside awireless communication device to another device. The management frame isa frame used to manage a communication links with other terminals. Asexamples, a beacon frame, an association request frame, an associationresponse frame and the like are given. The control frame is a frame usedto perform control at the time of transmitting/receiving (exchanging) amanagement frame and a data frame to/from another wireless communicationdevice. As examples, an RTS (Request to Send) frame, a CTS (Clear toSend) frame, an ACK frame and the like are given.

Further, if interference has occurred in the operation channel, thecommunication controller 17 decides a radiation pattern selection policyaccording to the state of the interference, as the control of theradiation pattern. As an example, the communication controller 17selects a policy from among a plurality of policies. The communicationcontroller 17 changes the radiation pattern in accordance with theselected policy.

Further, the communication controller 17 decides to change the operatingchannel according to the state of the interference. In the case ofchanging the operating channel, a channel switching signal specifying achannel after change is transmitted. In more detail, a frame whichincludes the channel switching instruction specifying the channel afterchange is generated and transmitted. As a specific example of the frame,a beacon frame may be used, or a management frame different from thebeacon frame may be used. Transmission of the frame is performed in aprocedure in accordance with the CSMA/CA. Accompanying the change of theoperating channel, the communication controller 17 changes settings fora transmission filter and a reception filter of the communicator 15.

The storage 14 holds association information (or table information) inwhich radiation patterns and pieces of antenna setting information areassociated. The radiation patterns are given identifiers in advance.Each piece of antenna setting information indicates antenna settingsrequired to obtain a corresponding radiation pattern. For example, eachof a plurality of antennas has a plurality of branches, the antennasetting information includes, for each of the plurality of antennas, avalue indicating an impedance value (or a resistance value) of eachbranch. Further, the storage 14 may store information about directivity(a direction, an angle or the like) of each radiation pattern. Thesepieces of information may be set during manufacture or at the shipmentof a product, or the wireless communication device 1 may set the piecesof information in the storage 14 by receiving an instruction to set thepieces of information from an external device. The external device maybe a device of a user of the wireless communication device 1 or may be aserver.

Further, the storage 14 stores a history of use of radiation patterns bythe wireless communication device 1 (hereinafter referred to as aradiation pattern history). As an example, in the radiation patternhistory, the number of times of selection, transmission success rate,communication quality and the like of each radiation pattern are storedbeing classified for each channel. As an example of the communicationquality, an RSSI (Received Signal Strength Indicator) and an SN (Signalto Noise) ratio are given. The communication quality may be either anaverage value or a latest value. In the radiation pattern history,information about time at which and order in which each radiationpattern is used may be stored being classified for each channel. Theradiation pattern history is updated by the communication controller 17,by the antenna switcher 16 or by both of them. For example, each timecommunication is performed, the communication controller 17 updates theradiation pattern history based on a radiation pattern used for thecommunication, the current channel and a result of the communication.

Here, examples of the policy will be shown. For example, there is apolicy for selecting a radiation pattern based on the radiation patternhistory stored in the storage 14 (a history use policy). Further, thereis a policy for randomly selecting a radiation pattern from among aplurality of radiation patterns which can be set for the variableantenna portion 11 (a random policy). Further, there is a policy forselecting a radiation pattern having directivity in a specifieddirection or a particular direction (a directivity policy). Further,there is a policy, by switching all the radiation patterns in turn andmeasuring communication quality (such as the S/N ratio), selecting aradiation pattern from which the highest communication quality orcommunication quality equal to or higher than a threshold is obtained(an actual measurement policy). The measurement of the communicationquality can be performed by the communication controller 17 or theinterference detector 10. As an example of other policies, there is apolicy for selecting a predetermined radiation pattern or selecting aradiation pattern in predetermined priority order (a prespecifiedpolicy). The predetermined radiation pattern may be, for example, theomnidirectional radiation pattern or a radiation pattern other than theomnidirectional radiation pattern.

Each policy may be divided into more detail classifications. Forexample, the history use policy includes: a policy for selecting aradiation pattern based on the number of times of selection in the past(a number-of-selections policy); a policy for selecting a radiationpattern based on communication success probability (a success ratepolicy); and a policy for selecting a radiation pattern based oncommunication quality (a communication quality policy). In addition,there is a policy for selecting a radiation pattern which is notincluded in the radiation pattern history, and a policy obtained bycombining these policies. In the number-of-selections policy, aradiation pattern which has been selected many times may bepreferentially selected. In the success rate policy, a radiation patternwith a high success probability may be preferentially selected, or aradiation pattern with a success probability equal to or above athreshold may be preferentially selected. If, in the case of using thehistory use policy, the radiation pattern history is empty, or acorresponding radiation pattern does not exist, a predetermined defaultradiation pattern may be selected. As the default radiation pattern, forexample, the omnidirectional radiation pattern or a radiation patternother than the omnidirectional radiation pattern may be used. The policyexamples shown here are mere examples, and other various policies can bedefined.

Each policy may be stored in the storage 14 or may be stored in thecommunication controller 17. Each policy may exist in a form of data ormay exist in a form of a program (logic).

The communicator 15 performs processing related to the PHY layer(physical layer) of a communication protocol and radio processing.Specifically, as the PHY layer processing, addition of a PHY header to aframe, encoding of the frame, modulation of encoded data and the like atthe time of transmission are included. The radio processing includesprocessing such as DA (Digital to Analog) conversion of a modulatedsignal, band control by the transmission filter, and up-conversion andamplification of an analog signal. At the time of reception, low-noiseamplification of a signal received via an antenna, down-conversion ofthe amplified signal, band control of the down-converted signal by thereception filter (extraction of a signal of the operating channel) andthe like are performed as radio processing. Filter processing forperforming band control of the wireless LAN system (extraction ofsignals of all bands used by the system) may be performed before thedown-conversion. The PHY layer processing includes processing such asdemodulation and decoding of the band-controlled signal, and analysis(removal) of a physical header.

The functions of the controller 12, the interference detector 10 and thecommunicator 15 may be performed by software (a program) operating on aprocessor such as a CPU, or by hardware, or by both of the software andthe hardware. The software may be stored in a storage medium such as amemory such as a ROM and a RAM, a hard disk and an SSD, and read andexecuted by the processor.

The storage 14 may be a memory or may be an SSD, a hard disk or thelike. The memory may be a volatile memory such as an SRAM and a DRAM ora nonvolatile memory such as a NAND and an MRAM. Though the storage 14is shown as an independent block in FIG. 1, it may exist in the antennaswitcher 16 or the communication controller 17 or may be distributedlyarranged in the antenna switcher 16 and the communication controller 17.

FIG. 2 is a block diagram showing a configuration example of theinterference detector 10. The interference detector 10 is provided witha signal detector 100 and a signal recognizer 110.

The signal detector 100 generates data of a relationship between timeand frequency (time-frequency data) by a receive signal being inputtedfrom the variable antenna portion 11 and the signal detector 100analyzing the receive signal. The time-frequency data can be generated,for example, by performing AD conversion and FFT (Fast FourierTransform) processing of the receive signal. The time-frequency data maybe generated in other methods. FIG. 3 shows an example of thetime-frequency data. In this example, the time-frequency data includesfour waveforms.

A waveform 51 shows that a radio wave with a width of 1 MHz has beencontinuously received on the low frequency band side. This is a patternwhich is seen in a case of output of an analog apparatus such as ananalog video recorder, an analog cordless telephone and a jammer(hereinafter, the pattern may be called a continuous wave pattern). Awaveform 52 has such a pattern that a frequency cyclically repeatschanging at a certain inclination as time progresses, and it is apattern seen in a case of a radar and the like. In a waveform 53, shortpulse-shaped signals randomly appear in a certain frequency band. It isa pattern seen in a case of a Bluetooth® apparatus and the like whichperform frequency hopping. In a waveform 54, signals occupying a certainfrequency band intermittently appear. It is a pattern seen in a wirelesscommunication device such as a wireless LAN communication device inconformity with IEEE 802.11.

The signal recognizer 110 receives the time-frequency data generated bythe signal detector 100 and, by analyzing the time-frequency data,grasps a characteristic of an interference signal existing in afrequency range targeted by analysis. Here, a category of a device whichis an interference signal occurrence source (an interference source) isgrasped as the characteristic of the interference signal. For thispurpose, the signal recognizer 110 is provided with a classifier 111 anda database 112. The analysis may be performed for the whole frequencyrange targeted by the analysis or may be performed for each of dividedbands (channels) obtained by dividing the frequency range into bandscorresponding to channels.

The classifier 111 calculates a plurality of features based on thetime-frequency data. As examples of the features, a spectral shapefeature, a value or a range showing a rate of time during which a signalis at a high level (a level equal to or higher than a threshold), apulse shape feature, a degree of pulse spread and the like are given.These features are mere examples, and various features which areeffective to judge a device category may be defined. FIG. 4(A)schematically shows the kinds of the features. The classifier 111identifies the category of the interference-source device based on theplurality of features. As examples of the device category, categoriessuch as analog apparatus (analog video recorder, analog cordlesstelephone, jammer and the like), Bluetooth apparatus, wireless LANdevice (Wi-Fi device), radar device and the like are conceivable. Theclassifier 111 decides any of these categories as the classification ofthe interference-source device. Such classification processing can beperformed with the use of an arbitrary model. As an example of themodel, a binary tree can be used. An example of the binary tree isschematically shown in FIG. 4(B).

The binary tree in FIG. 4(B) is provided with a top node 1, lowest nodes2, 4 and 5, and an intermediate node 3 other than the top node and thelowest nodes. Processing using one or a plurality of features isassigned to each of the nodes 1 and 3 other than the lowest nodes. Theprocessing is started for the top node 1 and is branched to any lowernode (child node) according to a processing result. This is repeateduntil the lowest nodes are reached. Device categories, which arejudgment results, are assigned to the lowest nodes 2, 4 and 5. Forexample, analog apparatus, Wi-Fi device and radar device are assigned tothe node 2, 4 and 5, respectively. The device categories assigned to thereached lowest nodes are decided as the classifications of theinterference-source devices.

As an example of processing at the nodes, operation using one or morefeatures is performed, and the processing proceeds to any of a pluralityof child nodes according to a result of the operation. For example, itis judged whether a feature or a value obtained by the operation basedon the feature is larger than a first value or not, and the processingbranches to a first child node if the feature or the value is largerthan the first value, and branches to a second child node if the featureor the value is equal to or smaller than the first value. Though thenumber of child nodes is two in FIG. 4(B), the number may be three ormore. The database 112 stores data of the binary tree, a featurecalculation formula and the like.

Such a binary tree can be generated by machine learning. For example,signals are received from one or more devices the categories of whichare known in advance; a plurality of features are calculated from thereceived signal, and the calculated plurality of features areaccumulated in association with the device categories. By performingmachine learning of the data acquired for the plurality of categories ofdevices, a model for identifying a device category from a plurality offeatures can be generated.

The model to be used is not limited to a binary tree. Other models suchas a neural network are also possible.

Here, an example of identifying a device category has been shown as amethod for grasping a characteristic of an interference signal. Asanother method, it is also possible to prepare a plurality of waveformpatterns as templates and identify which waveform pattern aninterference signal has. For example, it is also possible to calculate adegree of similarity between waveform data obtained by analyzing areceive signal and each template and identify a waveform pattern withthe highest similarity degree. The waveform data may be normalizedbefore calculation of the similarity degree. As for calculation of thesimilarity degree between waveforms, a general algorithm for calculatinga distance between waveforms can be used, and the similarity degree canbe determined based on the calculated distance. As an example, thesimilarity degree may be defined so that the similarity degree becomes alarger value as the distance is smaller. The analysis may be performedfor each of divided bands (channels) obtained by dividing the frequencyrange into bands corresponding to channels.

Next, a channel switching process of the wireless communication device 1according to the present embodiment will be described. FIGS. 5 and 6 area flowchart of the channel switching process of the wirelesscommunication device 1. In the description below, it is assumed that thewireless communication device 1 uses a channel A as the operatingchannel.

As shown in FIG. 5, the communication controller 17 selects a radiationpattern in accordance with a predetermined policy and instructs theantenna switcher 16 to set the selected radiation pattern. The antennaswitcher 16 sets the variable antenna portion 11 to a configurationcorresponding to the radiation pattern (step S10). At step S10, the caseof using the history use policy is assumed.

When the radiation pattern is set by the antenna switcher 16, thecommunication controller 17 performs communication using the channel Avia the communicator 15 (step S11). In a case of newly transmitting aframe, the communication controller 17 acquires a right to access awireless medium in accordance with the CSMA/CA before transmitting theframe. Specifically, the communication controller 17 checks the state ofthe wireless medium by carrier sensing and, if the state is idle,acquires an access right and performs frame transmission. Further, whenreceiving a frame which requires an acknowledgement response, from acommunication partner terminal, the communication controller 17transmits an acknowledgement response frame (such as an ACK frame) aftera predetermined time after completion of reception of the frame.

The interference detector 10 detects whether radio wave interferencewith another device has occurred in the channel A, based on a signalreceived via the variable antenna portion 11 (step S12). For example,the interference detector 10 monitors a wireless medium for apredetermined time, and, if a signal with a level equal to or above athreshold (a signal with such a level that the wireless medium is judgedto be in a busy state) from a device outside the network formed by itsown device is detected during the time, judges that a radio waveinterference has occurred. The detection operation is performedindependently from (in parallel to) the communication of thecommunication controller 17. Whether or not the signal is from a devicebelonging to the network of its own device can be known, for example, byanalyzing the frame or the header of the frame. This analysis may beperformed by the interference detector 10, or the communicationcontroller 17 may perform the analysis and notify a result of theanalysis to the interference detector 10.

If the interference detector 10 does not detect occurrence ofinterference (step S12: No), the communication controller 17 maintainsthe current radiation pattern and continues the communication throughthe channel A (step S13).

On the other hand, if detecting occurrence of interference in thechannel A (step S12: Yes), the interference detector 10 identifies acharacteristic of an interference signal in the channel A (step S20).Specifically, the interference detector 10 identifies the devicecategory of an interference source, such as wireless LAN device (Wi-Fidevice), analog apparatus (such as analog cordless telephone and analogvideo recorder), Bluetooth device and radar device. Otherwise, asanother method, a waveform pattern may be identified as described above.The case of identifying a device category is assumed below. The numberof device categories to be identified is not limited to one but may bemore than one. Further, when it is possible to estimate the direction orposition of the interference source, or both of them, those may beidentified. For the estimation of the direction or position of theinterference source, a general arrival direction estimation algorithm orposition estimation algorithm can be used. At this time, a process forestimating the arrival direction and the position may be performed bythe interference detector 10 or by the communication controller 17.

Next, the interference detector 10 judges whether the duty ratio of theinterference source signal is high or not (step S21). The duty ratio isa rate of period during which signals with a level equal to or higherthan a threshold have been received, among signals received within apredetermined period. That the duty ratio is high means that the dutyratio is equal to or above a predetermined value.

If a device of a predetermined category defined as a device with a highduty ratio is detected, it is judged that the duty ratio of a signal ofthe interference source is high. Here, an analog apparatus (such as ananalog cordless telephone and an analog video) corresponds to such adevice. That is, an analog apparatus is an example of a device with ahigh duty ratio. In the case of identifying a waveform pattern at stepS20, the duty ratio of a signal of the interference source is judged tobe high if a waveform in a predetermined pattern, for example, acontinuous wave pattern like the waveform 51 in FIG. 3 is detected.

If it is judged that the duty ratio is not high (step S21: No), theinterference detector 10 sends information indicating that, thoughinterference has been detected in the channel A, it is not interferencewith a high duty ratio, to the communication controller 17. Whenreceiving this information, the communication controller 17 decides tochange the radiation pattern while deciding to continue the current useof the channel A. The communication controller 17 newly selects aradiation pattern for the channel A based on the current policy (thehistory use policy). The communication controller 17 outputs aninstruction signal to change the radiation pattern to the selectedradiation pattern to the antenna switcher 16. The antenna switcher 16sets the variable antenna portion 11 according to the specifiedradiation pattern (step S22).

For example, a radiation pattern for which an average of communicationquality (such as the SN ratio) is the highest or a radiation patternwith the highest communication success rate is identified. When theidentified pattern is the same as the currently used radiation pattern,the current radiation pattern may be maintained, or a radiation patternwith the second highest value may be newly selected. As another exampleof selection using the radiation pattern history, it is also possible toidentify data for which the same radiation pattern as the radiationpattern currently used was used in the past and, if the communicationsuccess rate or SN ratio of the identified radiation pattern afterswitching to the identified radiation pattern is equal to or above apredetermined value, select the same radiation pattern as the identifiedpattern.

After the radiation pattern of the variable antenna portion is changed,the communication controller 17 performs communication through thechannel A via the communicator 15 (step S23). The communicationcontroller 17, the antenna switcher 16, or both of them update theradiation pattern history based on the radiation pattern after thechange and a result of the communication (success or failure, or thelike).

FIG. 7 shows a state in which the operating channel A of the wirelesscommunication device 1 interferes with a radio wave outputted fromanother communication device 2. In this example, near a wireless LANsystem constituted by the wireless communication device 1 correspondingto an access point and terminals 3A, 3B, 3C and 3D, the othercommunication device 2 of a different system exists. It is assumed thatthe wireless communication device 1 uses the omnidirectional radiationpattern. It is assumed that the other communication device 2 is a devicewhich outputs a signal with a duty ratio which is not high. Here, theother communication device 2 is assumed to be an adjacent access pointor a terminal belonging to the access point. A circular dotted line 8indicates an area of a radio wave outputted from the other communicationdevice 2. The wireless communication device 1 exists within the area anddetects the interference of the channel A.

FIG. 8 is a diagram showing a radiation pattern of the wirelesscommunication device 1 after the other communication device 2 is judgednot to be an interference source with a high duty ratio at step S21 inthe state of FIG. 7, and the radiation pattern is changed at step S22. Along dashed and short dashed line 31 in FIG. 8 indicates the radiationpattern of the wireless communication device 1. In an area of theradiation pattern, the terminals 3A and 3B are included, but theterminals 3C and 3D and the other communication device 2 are notincluded. Since the wireless communication device 1 does not receive aradio wave of the other communication device 2 (does not detect areceive signal from the other communication device 2), the wirelesscommunication device 1 can communicate with the terminals 3A and 3Bwhile continuously using the channel A. However, the wirelesscommunication device 1 cannot communicate with the terminals 3C and 3D.

On the other hand, if judging that an interference source with a highduty ratio exists (step S21: Yes), the interference detector 10 sendsinformation notifying that interference has been detected in the channelA, and it is interference with a high duty ratio, to the communicationcontroller 17.

When receiving this information, the communication controller 17 judgeswhether a free channel exists by checking radio wave reception states ofone or more candidate channels other than the channel A (step S30). Thejudgment about whether a free channel exists can be performed in anarbitrary method. For example, it is possible to monitor a candidatechannel for a predetermined time and, if a signal with a predeterminedor higher level is not received, judge that the candidate channel is afree channel. Checking on whether a free channel exists or not may beperformed by the interference detector 10. In this case, thecommunication controller 17 outputs an instruction signal to instructthe interference detector 10 to determine whether a free channel existsor not to the interference detector 10, and the interference detector 10determines whether a free channel exists or not and feeds back a resultof the determination.

If judging that there is a free channel among the candidate channelsother than the channel A (step S30: Yes), the communication controller17 decides the detected free channel as a change-destination channel(hereinafter referred to as a channel B) to replace the channel A. Thefree channel may be a free channel detected earliest. If a plurality offree channels are detected, a channel with the highest communicationquality may be selected.

The communication controller 17 changes the policy to the random policyand randomly selects a radiation pattern, that is, selects an arbitraryradiation pattern in accordance with the random policy. Thecommunication controller 17 sets the selected radiation pattern for thevariable antenna portion 11 via the antenna switcher 16 (step S40). Thatis, since it is unknown which radiation pattern can be selected to avoidinfluence of the interference source and acquire a right to access awireless medium, a radiation pattern is randomly selected.

After the radiation pattern of the variable antenna portion 11 ischanged, the communication controller 17 transmits a channel switchingsignal through the channel A before changing the operating channel (stepS41). In more detail, a frame which includes information specifyingchannel switching to the channel B is generated, and the frame istransmitted. As an example of the frame instructing channel switching, abeacon frame may be used, or a management frame different from thebeacon frame may be used. Transmission of the frame is performed in aprocedure in accordance with the CSMA/CA. That is, carrier sensing of awireless medium is performed; and, if a result of the carrier sensingshows an idle state, the right to access the wireless medium isacquired, and the frame is transmitted. If the channel state is a busystate, and it is not possible to acquire the access right even if apredetermined period elapses, it is also possible to return to step S40and newly select a radiation pattern under the random policy.Information indicating a timing of performing channel switching may beset for the transmitted frame. The channel switching timing informationmay be transmitted by a different frame.

The communication controller 17 switches the operating channel from thechannel A to the channel B at a predetermined switching timing and,after that, performs communication through the channel B (step S42). Apolicy used at the time of starting communication through the channel Bmay be the prespecified policy (for selecting a predetermined radiationpattern or selecting a radiation pattern in predetermined priorityorder), or the random policy may be continuously used. Other policiesmay be used. When there is a radiation pattern history of the channel B,the history use policy may be used.

The communication controller 17 may switch the operating channel to thechannel B after repeating steps S40 and S41 a plurality of times.Thereby, a possibility of transmitting a channel switching signal inmore radiation patterns is strengthened, and a possibility of being ableto notify channel switching to as many terminals as possible isstrengthened. However, when the number of times is large, a timerequired before actually changing the channel is longer, and, therefore,it becomes difficult to perform channel change rapidly. Therefore, thenumber of times of repeating steps S40 and S41 may be restricteddepending on a duration allowed before the channel is changed.

FIG. 9 is a diagram illustrating a specific example of steps S40 andS41. The operating channel A of the wireless communication device 1interferes with a radio wave outputted from another communication device7. In this example, near the wireless LAN system constituted by thewireless communication device 1 corresponding to an access point and theterminals 3A, 3B, 3C and 3D, the other communication device 7 of adifferent system exists. It is assumed that the wireless communicationdevice 1 uses the omnidirectional radiation pattern. It is assumed thatthe other communication device 7 is a device with a high duty ratio, forexample, an analog apparatus such as an analog video camera. A circulardotted line 9 indicates an area of a radio wave outputted from theanother communication device 7. The wireless communication device 1exists within the area and detects the interference of the channel A.

As a result of the wireless communication device 1 having changed theradiation pattern at step S40, a radiation pattern indicated by a longdashed and short dashed line 32 in FIG. 9 is set. The wirelesscommunication device 1 transmits a channel switching signal via thechannel A in this radiation pattern. Since the terminals 3A and 3B areincluded in the area of the radiation pattern and not included in aradio wave area of the other communication device 7, the terminals 3Aand 3B succeed in reception of the channel switching signal. Since theterminal 3C is included in the radio wave area of the othercommunication device 7, whether the terminal 3C succeeds in reception ofthe channel switching signal depends on directivity of the terminal 3C.Here, it is assumed that the terminal 3C has not succeeded in receptionof the channel switching signal. Since the terminal 3D is not includedin the radiation pattern of the wireless communication device 1, theterminal 3D does not receive the channel switching signal. For example,the terminals 3A and 3B which have succeeded in reception of the channelswitching signal switch operating channels to the channel B, which is afree channel specified by the wireless communication device 1, at apre-specified timing. FIG. 10 is a diagram showing a state in which thewireless communication device 1 and the terminals 3A and 3B haveswitched the operating channels from the channel A to the channel B. InFIG. 10, the wireless communication device 1 and the terminals 3A and 3Bare surrounded by broken-line rectangles. This means that the operatingchannels have been switched to the channel B. As for the terminals 3Cand 3D, the channel A is still set.

FIG. 11 shows a state in which the terminals 3C and 3D which havedetected that it is impossible to communicate with the wirelesscommunication device 1 through the channel A have identified the channelB, which is the operating channel of the wireless communication device1, by channel search and switched operating channels to the channel B.The terminals 3C and 3D execute an association process with the wirelesscommunication device 1 again through the channel B and belong to thenetwork formed by the wireless communication device 1. Since theoperating channels of the terminals 3C and 3D have been switched to thechannel B, the terminals 3C and 3D are surrounded by broken-linerectangles in FIG. 11. The wireless communication device 1 and theterminals 3A to 3D can perform communication without interfering withthe other communication device 7.

On the other hand, if judging that a free channel does not exist amongthe candidate channels other than the channel A (step S30: No), thecommunication controller 17 resets the radiation pattern history storedin the storage 14. Further, the communication controller 17 switches theused policy to the random policy and selects an arbitrary radiationpattern in accordance with the random policy. The communicationcontroller 17 instructs the antenna switcher 16 to change the radiationpattern to the selected radiation pattern, and the antenna switcher 16sets the specified radiation pattern for the variable antenna portion 11(step S31). The communication controller 17 performs communicationthrough the channel A (S32). The radiation pattern which has been set, aresult of the communication and the like are registered with theradiation pattern history (step S33). Thereby, the radiation patternhistory is updated.

Though the history use policy is continuously used to select a radiationpattern at step S22 in FIG. 5, the history use policy may be changed toa different policy. For example, when the number of times that it isjudged at step S12 that interference has occurred reaches apredetermined value within a predetermined time, the policy may bechanged.

A modification of the process described above will be shown.

(First Modification)

FIG. 12 is a flowchart according to a first modification. Step S20 inFIG. 5 is replaced with step S51. Though a device category is identifiedat step S20 in FIG. 5, a duty value is calculated at step S51 in thepresent flow. Specifically, a period during which signals with a levelequal to or higher than a threshold have been received, among signalsreceived within a predetermined period is calculated. Then, a rate ofthe calculated duration to the predetermined duration is calculated.Thereby, a duty ratio is obtained. At the next step S21, it is judgedwhether or not the duty ratio is equal to or above a predeterminedvalue. If the duty ratio is equal to or above the predetermined value,it is judged that interference with a high duty ratio exists, and theflow proceeds to step S30. If the duty ratio is below the predeterminedvalue, it is judged that interference with a high duty ratio does notexist, and the flow proceeds to step S22. Processes of steps other thansteps S30 and S22 may be similar to those described above.

(Second Modification)

At the time of changing the policy (to the random selection) at step S40in FIG. 6, a reception judgment threshold (for example, CCA (ClearChannel Assessment) threshold) used in carrier sensing may be increased.As an example, a first threshold is changed to a second threshold largerthan the first threshold.

For example, it is assumed that the communicator 15 detects signalreception when receiving a signal with a level equal to or above thefirst threshold but does not detect signal reception even if receiving asignal with a level below the first threshold. That is, in the case of asignal with a level equal to or above the first threshold, it is judgedthat a wireless medium is in a busy state, and, in the case of a signalwith a level below the first threshold, it is judged that the wirelessmedium is in an idle state. By increasing the first threshold to thesecond threshold at step S40, even if a signal with a level equal to orabove the first threshold is received, the wireless medium is judged tobe in an idle state when the level of the signal is below the secondthreshold. Therefore, even if a signal is received from the othercommunication device 7 during carrier sensing, the wireless medium isjudged to be idle if the level of the signal is below the secondthreshold, and it is possible to transmit a channel switching signal. Atstep S31 in FIG. 6, at step S22 in FIG. 5 or at both of the steps, thereception judgment threshold may be increased at the time of changingthe radiation pattern.

Though the threshold is increased accompanying change of the policyhere, the threshold may be increased without changing the policy. Aflowchart in this case will be shown in FIG. 13. Step S40 in FIG. 5 isreplaced with step S52. At step S52, the reception judgment threshold isincreased while the current radiation pattern is maintained. As anexample, the first threshold is changed to the second threshold largerthan the first threshold. For step S31, for step S22 in FIG. 5 or forboth of the steps, the reception judgment threshold may be similarlyincreased without changing the radiation pattern.

(Third Modification)

Though the description so far has been made on the assumption that adevice which outputs a signal with a high duty is an analog apparatussuch as a video camera, there is a possibility that the device is acommunication device adopting an LBT scheme other than a wireless LANcommunication device. If the possibility exists, it is also possible toselect not the random policy but the directivity policy (for selecting aradiation pattern having directivity in a specified direction or aparticular direction) as a policy and set such a radiation pattern thatthe directivity is toward the communication device at step S40. Bycausing the directivity to be toward the communication device, thecommunication device can detect a signal transmitted by the wirelesscommunication device 1. The communication device which detects thesignal can set a transmission prohibited period (referred to as NAV(Network Allocation Vector) in the case of wireless LAN) to suppressframe transmission. In a case where an access right cannot be acquiredby carrier sensing within a predetermined period, however, the policymay be returned to the random policy. At step S40, it is also possibleto select a policy other than the random policy and the directivitypolicy described above.

As described above, according to the present embodiment, when anothercommunication device with a high duty ratio exists, the wirelesscommunication device 1 can rapidly select a radiation pattern capable ofpreventing interference with the other communication device, by changingthe policy. As an example, by changing the history use policy to therandom policy, a radiation pattern capable of avoiding interference canbe selected rapidly. By transmitting a channel switching signal in aradiation pattern selected in this way, it is possible to notify channelchange rapidly. Terminals which receive the channel switching signal canperform channel switching without performing an association process withthe wireless communication device 1 again through a channel after theswitching. Terminals which cannot receive the channel switching signal(terminals not included in the area of a changed radiation pattern) arerequired to search for the wireless communication device 1 by channelsearch and perform an association process but can continuouslycommunicate with the wireless communication device 1 after channelchange.

Second Embodiment

FIG. 14 is a functional block diagram of a base station (access point)400 according to a second embodiment. The access point includes acommunication processor 401, a transmitter 402, a receiver 403, antennas42A, 42B, 42C, and 42D, a network processor 404, a wired I/F 405, and amemory 406. The access point 400 is connected to a server 407 throughthe wired I/F 405. The communication processor 401 has functions similarto the controller 12 and the interference detector 10 described in thefirst embodiment. The transmitter 402 and the receiver 403 havefunctions similar to the communicator 15 described in the firstembodiment. The network processor 404 has functions similar to thehigher processor 90 described in the first embodiment. The communicationprocessor 401 may internally possess a buffer for transferring data toand from the network processor 404. The buffer may be a volatile memory,such as an SRAM or a DRAM, or may be a non-volatile memory, such as aNAND or an MRAM.

The network processor 404 controls data exchange with the communicationprocessor 401, data writing and reading to and from the memory 406, andcommunication with the server 407 through the wired I/F 405. The networkprocessor 404 may execute a higher communication process of the MAClayer, such as TCP/IP or UDP/IP, or a process of the application layer.The operation of the network processor may be performed throughprocessing of software (program) by a processor, such as a CPU. Theoperation may be performed by hardware or may be performed by both ofthe software and the hardware.

For example, the communication processor 401 corresponds to a basebandintegrated circuit, and the transmitter 402 and the receiver 403correspond to an RF integrated circuit that transmits and receivesframes. The communication processor 401 and the network processor 404may be formed by one integrated circuit (one chip). Parts that executeprocessing of digital areas of the transmitter 402 and the receiver 403and parts that execute processing of analog areas may be formed bydifferent chips. The communication processor 401 may execute a highercommunication process of the MAC layer, such as TCP/IP or UDP/IP.Although the number of antennas is four here, it is only necessary thatat least one antenna is included.

The memory 406 saves data received from the server 407 and data receivedby the receiver 402. The memory 406 may be, for example, a volatilememory, such as a DRAM, or may be a non-volatile memory, such as a NANDor an MRAM. The memory 406 may be an SSD, an HDD, an SD card, an eMMC,or the like. The memory 406 may be provided outside of the base station400.

The wired I/F 405 transmits and receives data to and from the server407. Although the communication with the server 407 is performed througha wire in the present embodiment, the communication with the server 407may be performed wirelessly. In this case, a wireless I/F may beemployed instead of the wired I/F 405.

The server 407 is a communication device that returns a responseincluding requested data in response to reception of a data forwardrequest for requesting transmission of the data. Examples of the server407 include an HTTP server (Web server) and an FTP server. However, theserver 407 is not limited to these as long as the server 407 has afunction of returning the requested data. The server 407 may be acommunication device operated by the user, such as a PC or a smartphone.

When the STA belonging to the BSS of the base station 400 issues aforward request of data for the server 407, a packet regarding the dataforward request is transmitted to the base station 400. The base station400 receives the packet through the antennas 42A to 42D. The basestation 400 causes the receiver 403 to execute the process of thephysical layer and the like and causes the communication processor 401to execute the process of the MAC layer and the like.

The network processor 404 analyzes the packet received from thecommunication processor 401. Specifically, the network processor 404checks the destination IP address, the destination port number, and thelike. When the data of the packet is a data forward request such as anHTTP GET request, the network processor 404 checks whether the datarequested by the data forward request (for example, data in the URLrequested by the HTTP GET request) is cached (stored) in the memory 406.A table associating the URL (or reduced expression of the URL, such as ahash value or an identifier substituting the URL) and the data is storedin the memory 406. The fact that the data is cached in the memory 406will be expressed that the cache data exists in the memory 406.

When the cache data does not exist in the memory 406, the networkprocessor 404 transmits the data forward request to the server 407through the wired I/F 405. In other words, the network processor 404substitutes the STA to transmit the data forward request to the server407. Specifically, the network processor 404 generates an HTTP requestand executes protocol processing, such as adding the TCP/IP header, totransfer the packet to the wired I/F 405. The wired I/F 405 transmitsthe received packet to the server 407.

The wired I/F 405 receives, from the server 407, a packet that is aresponse to the data forward request. From the IP header of the packetreceived through the wired I/F 405, the network processor 404 figuresout that the packet is addressed to the STA and transfers the packet tothe communication processor 401. The communication processor 401executes processing of the MAC layer and the like for the packet. Thetransmitter 402 executes processing of the physical layer and the likeand transmits the packet addressed to the STA from the antennas 42A to42D. The network processor 404 associates the data received from theserver 407 with the URL (or reduced expression of the URL) and saves thecache data in the memory 406.

When the cache data exists in the memory 406, the network processor 404reads the data requested by the data forward request from the memory 406and transmits the data to the communication processor 401. Specifically,the network processor 404 adds the HTTP header or the like to the dataread from the memory 406 and executes protocol processing, such asadding the TCP/IP header, to transmit the packet to the communicationprocessor 401. In this case, the transmitter IP address of the packet isset to the same IP address as the server, and the transmitter portnumber is also set to the same port number as the server (destinationport number of the packet transmitted by the communication terminal),for example. Therefore, it can be viewed from the STA as ifcommunication with the server 407 is established. The communicationprocessor 401 executes processing of the MAC layer and the like for thepacket. The transmitter 402 executes processing of the physical layerand the like and transmits the packet addressed to the STA from theantennas 42A to 42D.

According to the operation, frequently accessed data is responded basedon the cache data saved in the memory 406, and the traffic between theserver 407 and the base station 400 can be reduced. Note that theoperation of the network processor 404 is not limited to the operationof the present embodiment. There is no problem in performing otheroperation when a general caching proxy is used, in which data isacquired from the server 407 in place of the STA, the data is cached inthe memory 406, and a response is made from the cache data of the memory406 for a data forward request of the same data.

The base station (access point) according to the present invention canbe applied for the base station in the first embodiment. Thetransmission of the frame, the data or the packet used in firstembodiment may be carried out based on the cached data stored in thememory 406. Also, information obtained based on the frame, the data orthe packet received by the base station in first embodiment may becached in the memory 406. The frame transmitted by the base station inthe first embodiment may include the cached data or information based onthe cached data. The information based on the cached data may includeinformation on existence or non-existence of data addressed to theterminal, information on a size of the data, a size of a packet requiredfor transmission of the data. The information based on the cached datamay include a modulation scheme required for transmission of the data.

In the present embodiment, although the base station with the cachefunction is described, a terminal (STA) with the cache function can alsobe realized by the same block configuration as FIG. 14. The terminalmeans non-base station terminal (as stated above, the base station isone form of the wireless communication terminal). In this case, thewired I/F 405 may be omitted. The transmission, by the terminal, of theframe, the data or the packet used in first embodiment may be carriedout based on the cached data stored in the memory 406. Also, informationobtained based on the frame, the data or the packet received by theterminal in first embodiment may be cached in the memory 406. The frametransmitted by the terminal in the first embodiment may include thecached data or information based on the cached data. The informationbased on the cached data may include information on existence ornon-existence of data addressed to the terminal, information on a sizeof the data, a size of a packet required for transmission of the data.The information based on the cached data may include a modulation schemerequired for transmission of the data.

Third Embodiment

FIG. 15 shows an example of entire configuration of a terminal or a basestation. The example of configuration is just an example, and thepresent embodiment is not limited to this. The terminal or the basestation includes one or a plurality of antennas 1 to n (n is an integerequal to or greater than 1), a wireless LAN module 148, and a hostsystem 149. The wireless LAN module 148 corresponds to the wirelesscommunication device according to the first embodiment. The wireless LANmodule 148 includes a host interface and is connected to the host system149 through the host interface. Other than the connection to the hostsystem 149 through the connection cable, the wireless LAN module 148 maybe directly connected to the host system 149. The wireless LAN module148 can be mounted on a substrate by soldering or the like and can beconnected to the host system 149 through wiring of the substrate. Thehost system 149 uses the wireless LAN module 148 and the antennas 1 to nto communicate with external apparatuses according to an arbitrarycommunication protocol. The communication protocol may include theTCP/IP and a protocol of a layer higher than that. Alternatively, theTCP/IP may be mounted on the wireless LAN module 148, and the hostsystem 149 may execute only a protocol in a layer higher than that. Inthis case, the configuration of the host system 149 can be simplified.Examples of the present terminal include a mobile terminal, a TV, adigital camera, a wearable device, a tablet, a smartphone, a gamedevice, a network storage device, a monitor, a digital audio player, aWeb camera, a video camera, a projector, a navigation system, anexternal adaptor, an internal adaptor, a set top box, a gateway, aprinter server, a mobile access point, a router, an enterprise/serviceprovider access point, a portable device, a hand-held device, a vehicleand so on.

The wireless LAN module 148 (or the wireless communication device) mayhave functions of other wireless communication standards such as LTE(Long Term Evolution), LTE-Advanced (standards for mobile phones) aswell as the IEEE802.11.

FIG. 16 shows an example of hardware configuration of a wireless LANmodule. The configuration can also be applied when the wirelesscommunication device is mounted on either one of the terminal that is anon-base station and the base station. Therefore, the configuration canbe applied as an example of specific configuration of the wirelesscommunication device shown in FIG. 1. At least one antenna 247 isincluded in the example of configuration. When a plurality of antennasare included, a plurality of sets of a transmission system (216 and 222to 225), a reception system (217, 232 to 235), a PLL 242, a crystaloscillator (reference signal source) 243, and a switch 245 may bearranged according to the antennas, and each set may be connected to acontrol circuit 212. One or both of the PLL 242 and the crystaloscillator 243 correspond to an oscillator according to the presentembodiment.

The wireless LAN module (wireless communication device) includes abaseband IC (Integrated Circuit) 211, an RF (Radio Frequency) IC 221, abalun 225, the switch 245, and the antenna 247.

The baseband IC 211 includes the baseband circuit (control circuit) 212,a memory 213, a host interface 214, a CPU 215, a DAC (Digital to AnalogConverter) 216, and an ADC (Analog to Digital Converter) 217.

The baseband IC 211 and the RF IC 221 may be formed on the samesubstrate. The baseband IC 211 and the RF IC 221 may be formed by onechip. Both or one of the DAC 216 and the ADC 217 may be arranged on theRF IC 221 or may be arranged on another IC. Both or one of the memory213 and the CPU 215 may be arranged on an IC other than the baseband IC.

The memory 213 stores data to be transferred to and from the hostsystem. The memory 213 also stores one or both of information to betransmitted to the terminal or the base station and informationtransmitted from the terminal or the base station. The memory 213 mayalso store a program necessary for the execution of the CPU 215 and maybe used as a work area for the CPU 215 to execute the program. Thememory 213 may be a volatile memory, such as an SRAM or a DRAM, or maybe a non-volatile memory, such as a NAND or an MRAM.

The host interface 214 is an interface for connection to the hostsystem. The interface can be anything, such as UART, SPI, SDIO, USB, orPCI Express.

The CPU 215 is a processor that executes a program to control thebaseband circuit 212. The baseband circuit 212 mainly executes a processof the MAC layer and a process of the physical layer. One or both of thebaseband circuit 212 and the CPU 215 correspond to the communicationcontrol apparatus that controls communication, the controller thatcontrols communication, or controlling circuitry that controlscommunication.

At least one of the baseband circuit 212 or the CPU 215 may include aclock generator that generates a clock and may manage internal time bythe clock generated by the clock generator.

For the process of the physical layer, the baseband circuit 212 performsaddition of the physical header, coding, encryption, modulation process,and the like of the frame to be transmitted and generates, for example,two types of digital baseband signals (hereinafter, “digital I signal”and “digital Q signal”).

The DAC 216 performs DA conversion of signals input from the basebandcircuit 212. More specifically, the DAC 216 converts the digital Isignal to an analog I signal and converts the digital Q signal to ananalog Q signal. Note that a single system signal may be transmittedwithout performing quadrature modulation. When a plurality of antennasare included, and single system or multi-system transmission signalsequivalent to the number of antennas are to be distributed andtransmitted, the number of provided DACs and the like may correspond tothe number of antennas.

The RF IC 221 is, for example, one or both of an RF analog IC and a highfrequency IC. The RF IC 221 includes a filter 222, a mixer 223, apreamplifier (PA) 224, the PLL (Phase Locked Loop) 242, a low noiseamplifier (LNA) 234, a balun 235, a mixer 233, and a filter 232. Some ofthe elements may be arranged on the baseband IC 211 or another IC. Thefilters 222 and 232 may be bandpass filters or low pass filters. The RFIC 221 is connected to the antenna 247 through the switch 245.

The filter 222 extracts a signal of a desired band from each of theanalog I signal and the analog Q signal input from the DAC 216. The PLL242 uses an oscillation signal input from the crystal oscillator 243 andperforms one or both of division and multiplication of the oscillationsignal to thereby generate a signal at a certain frequency synchronizedwith the phase of the input signal. Note that the PLL 242 includes a VCO(Voltage Controlled Oscillator) and uses the VCO to perform feedbackcontrol based on the oscillation signal input from the crystaloscillator 243 to thereby obtain the signal at the certain frequency.The generated signal at the certain frequency is input to the mixer 223and the mixer 233. The PLL 242 is equivalent to an example of anoscillator that generates a signal at a certain frequency.

The mixer 223 uses the signal at the certain frequency supplied from thePLL 242 to up-convert the analog I signal and the analog Q signal passedthrough the filter 222 into a radio frequency. The preamplifier (PA)amplifies the analog I signal and the analog Q signal at the radiofrequency generated by the mixer 223, up to desired output power. Thebalun 225 is a converter for converting a balanced signal (differentialsignal) to an unbalanced signal (single-ended signal). Although thebalanced signal is handled by the RF IC 221, the unbalanced signal ishandled from the output of the RF IC 221 to the antenna 247. Therefore,the balun 225 performs the signal conversions.

The switch 245 is connected to the balun 225 on the transmission sideduring the transmission and is connected to the LNA 234 or the RF IC 221on the reception side during the reception. The baseband IC 211 or theRF IC 221 may control the switch 245. There may be another circuit thatcontrols the switch 245, and the circuit may control the switch 245.

The analog I signal and the analog Q signal at the radio frequencyamplified by the preamplifier 224 are subjected to balanced-unbalancedconversion by the balun 225 and are then emitted as radio waves to thespace from the antenna 247.

The antenna 247 may be a chip antenna, may be an antenna formed bywiring on a printed circuit board, or may be an antenna formed by usinga linear conductive element.

The LNA 234 in the RF IC 221 amplifies a signal received from theantenna 247 through the switch 245 up to a level that allowsdemodulation, while maintaining the noise low. The balun 235 performsunbalanced-balanced conversion of the signal amplified by the low noiseamplifier (LNA) 234. The mixer 233 uses the signal at the certainfrequency input from the PLL 242 to down-convert, to a baseband, thereception signal converted to a balanced signal by the balun 235. Morespecifically, the mixer 233 includes a unit that generates carrier wavesshifted by a phase of 90 degrees based on the signal at the certainfrequency input from the PLL 242. The mixer 233 uses the carrier wavesshifted by a phase of 90 degrees to perform quadrature demodulation ofthe reception signal converted by the balun 235 and generates an I(In-phase) signal with the same phase as the reception signal and a Q(Quad-phase) signal with the phase delayed by 90 degrees. The filter 232extracts signals with desired frequency components from the I signal andthe Q signal. Gains of the I signal and the Q signal extracted by thefilter 232 are adjusted, and the I signal and the Q signal are outputfrom the RF IC 221.

The ADC 217 in the baseband IC 211 performs AD conversion of the inputsignal from the RF IC 221. More specifically, the ADC 217 converts the Isignal to a digital I signal and converts the Q signal to a digital Qsignal. Note that a single system signal may be received withoutperforming quadrature demodulation.

When a plurality of antennas are provided, the number of provided ADCsmay correspond to the number of antennas. Based on the digital I signaland the digital Q signal, the baseband circuit 212 executes a process ofthe physical layer and the like, such as demodulation process, errorcorrecting code process, and process of physical header, and obtains aframe. The baseband circuit 212 applies a process of the MAC layer tothe frame. Note that the baseband circuit 212 may be configured toexecute a process of TCP/IP when the TCP/IP is implemented.

The baseband circuit 212 or the host interface 214 may change anoperation channel by switching setting of the filter 222 and filter 232.The baseband circuit 212 or the host interface 214 may change theradiation patter of the antenna 247 by changing the setting of theantenna 247. The baseband circuit 212 may include functions of theinterference detector 10 and the controller 12.

Fourth Embodiment

FIG. 17(A) and FIG. 17(B) are perspective views of wireless terminalaccording to the fourth embodiment. The wireless terminal in FIG. 17(A)is a notebook PC 301 and the wireless communication device (or awireless device) in FIG. 17(B) is a mobile terminal 321. Each of themcorresponds to one form of a terminal (which may indicate a basestation). The notebook PC 301 and the mobile terminal 321 are equippedwith wireless communication devices 305 and 315, respectively. Thewireless communication device provided in a terminal (which may indicatea base station) which has been described above can be used as thewireless communication devices 305 and 315. A wireless terminal carryinga wireless communication device is not limited to notebook PCs andmobile terminals. For example, it can be installed in a TV, a digitalcamera, a wearable device, a tablet, a smart phone, a gaming device, anetwork storage device, a monitor, a digital audio player, a web camera,a video camera, a projector, a navigation system, an external adapter,an internal adapter, a set top box, a gateway, a printer server, amobile access point, a router, an enterprise/service provider accesspoint, a portable device, a handheld device and a vehicle and so on.

Moreover, a wireless communication device installed in a terminal (whichmay indicate a base station) can also be provided in a memory card. FIG.18 illustrates an example of a wireless communication device mounted ona memory card. A memory card 331 contains a wireless communicationdevice 355 and a body case 332. The memory card 331 uses the wirelesscommunication device 355 for wireless communication with externaldevices. Here, in FIG. 18, the description of other installed elements(for example, a memory, and so on) in the memory card 331 is omitted.

Fifth Embodiment

In the fifth embodiment, a bus, a processor unit and an externalinterface unit are provided in addition to the configuration of thewireless communication device according to any of the above embodiments.The processor unit and the external interface unit are connected with anexternal memory (a buffer) through the bus. A firmware operates theprocessor unit. Thus, by adopting a configuration in which the firmwareis included in the wireless communication device, the functions of thewireless communication device can be easily changed by rewriting thefirmware. The processing unit in which the firmware operates may be aprocessor that performs the process of the communication controllingdevice or the control unit according to the present embodiment, or maybe another processor that performs a process relating to extending oraltering the functions of the process of the communication controllingdevice or the control unit. The processing unit in which the firmwareoperates may be included in the access point or the wireless terminalaccording to the present embodiment. Alternatively, the processing unitmay be included in the integrated circuit of the wireless communicationdevice installed in the access point, or in the integrated circuit ofthe wireless communication device installed in the wireless terminal.

Sixth Embodiment

In the sixth embodiment, a clock generating unit is provided in additionto the configuration of the wireless communication device according toany of the above embodiments. The clock generating unit generates aclock and outputs the clock from an output terminal to the exterior ofthe wireless communication device. Thus, by outputting to the exteriorthe clock generated inside the wireless communication device andoperating the host by the clock output to the exterior, it is possibleto operate the host and the wireless communication device in asynchronized manner.

Seventh Embodiment

In the seventh embodiment, a power source unit, a power sourcecontrolling unit and a wireless power feeding unit are included inaddition to the configuration of the wireless communication deviceaccording to any of the above embodiments. The power supply controllingunit is connected to the power source unit and to the wireless powerfeeding unit, and performs control to select a power source to besupplied to the wireless communication device. Thus, by adopting aconfiguration in which the power source is included in the wirelesscommunication device, power consumption reduction operations thatcontrol the power source are possible.

Eighth Embodiment

In the eighth embodiment, a SIM card is added to the configuration ofthe wireless communication device according to the above embodiments.For example, the SIM card is connected with at least any one of blocksin the wireless communication device in FIG. 1. Thus, by adopting aconfiguration in which the SIM card is included in the wirelesscommunication device, authentication processing can be easily performed.

Ninth Embodiment

In the ninth embodiment, a video image compressing/decompressing unit isadded to the configuration of the wireless communication deviceaccording to any of the above embodiments. The video imagecompressing/decompressing unit is connected to the bus. Thus, byadopting a configuration in which the video imagecompressing/decompressing unit is included in the wireless communicationdevice, transmitting a compressed video image and decompressing areceived compressed video image can be easily done.

Tenth Embodiment

In the tenth embodiment, an LED unit is added to the configuration ofthe wireless communication device according to any of the aboveembodiments. For example, the LED unit is connected at least any one ofblocks in the wireless communication device in FIG. 1. Thus, by adoptinga configuration in which the LED unit is included in the wirelesscommunication device, notifying the operation state of the wirelesscommunication device to the user can be easily done.

Eleventh Embodiment

In the eleventh embodiment, a vibrator unit is included in addition tothe configuration of the wireless communication device according to anyof the above embodiments. For example, the vibrator unit is connected atleast any one of blocks in the wireless communication device in FIG. 1.Thus, by adopting a configuration in which the vibrator unit is includedin the wireless communication device, notifying the operation state ofthe wireless communication device to the user can be easily done.

Twelfth Embodiment

In the present embodiment, [1] the frame type in the wirelesscommunication system, [2] a technique of disconnection between wirelesscommunication devices, [3] an access scheme of a wireless LAN system and[4] a frame interval of a wireless LAN are described.

[1] Frame Type in Communication System

Generally, as mentioned above, frames treated on a wireless accessprotocol in a wireless communication system are roughly divided intothree types of the data frame, the management frame and the controlframe. These types are normally shown in a header part which is commonlyprovided to frames. As a display method of the frame type, three typesmay be distinguished in one field or may be distinguished by acombination of two fields. In IEEE 802.11 standard, identification of aframe type is made based on two fields of Type and Subtype in the FrameControl field in the header part of the MAC frame. The Type field is onefor generally classifying frames into a data frame, a management frame,or a control frame and the Subtype field is one for identifying moredetailed type in each of the classified frame types such as a beaconframe belonging to the management frame.

The management frame is a frame used to manage a physical communicationlink with a different wireless communication device. For example, thereare a frame used to perform communication setting with the differentwireless communication device or a frame to release communication link(that is, to disconnect the connection), and a frame related to thepower save operation in the wireless communication device.

The data frame is a frame to transmit data generated in the wirelesscommunication device to the different wireless communication deviceafter a physical communication link with the different wirelesscommunication device is established. The data is generated in a higherlayer of the present embodiment and generated by, for example, a user'soperation.

The control frame is a frame used to perform control at the time oftransmission and reception (exchange) of the data frame with thedifferent wireless communication device. A response frame transmittedfor the acknowledgment in a case where the wireless communication devicereceives the data frame or the management frame, belongs to the controlframe. The response frame is, for example, an ACK frame or a BlockACKframe. The RTS frame and the CTS frame are also the control frame.

These three types of frames are subjected to processing based on thenecessity in the physical layer and then transmitted as physical packetsvia an antenna. In IEEE 802.11 standard (including the extended standardsuch as IEEE Std 802.11ac-2013), an association process is defined asone procedure for connection establishment. The association requestframe and the association response frame which are used in the procedureare a management frame. Since the association request frame and theassociation response frame is the management frame transmitted in aunicast scheme, the frames causes the wireless communication terminal inthe receiving side to transmit an ACK frame being a response frame. TheACK frame is a control frame as described in the above.

[2] Technique of Disconnection Between Wireless Communication Devices

For disconnection of the connection (release), there are an explicittechnique and an implicit technique. As the explicit technique, a frameto disconnect any one of the connected wireless communication devices istransmitted. This frame corresponds to Deauthentication frame defined inIEEE 802.11 standard and is classified into the management frame.Normally, it is determined that the connection is disconnected at thetiming of transmitting the frame to disconnect the connection in awireless communication device on the side to transmit the frame and atthe timing of receiving the frame to disconnect the connection in awireless communication device on the side to receive the frame.Afterward, it returns to the initial state in a communication phase, forexample, a state to search for a wireless communication device of thecommunicating partner. In a case that the wireless communication basestation disconnects with a wireless communication terminal, for example,the base station deletes information on the wireless communicationdevice from a connection management table if the base station holds theconnection management table for managing wireless communicationterminals which entries into the BSS of the base station-self. Forexample, in a case that the base station assigns an AID to each wirelesscommunication terminal which entries into the BSS at the time when thebase station permitted each wireless communication terminal to connectto the base station-self in the association process, the base stationdeletes the held information related to the AID of the wirelesscommunication terminal disconnected with the base station and mayrelease the AID to assign it to another wireless communication devicewhich newly entries into the BSS.

On the other hand, as the implicit technique, it is determined that theconnection state is disconnected in a case where frame transmission(transmission of a data frame and management frame or transmission of aresponse frame with respect to a frame transmitted by the subjectdevice) is not detected from a wireless communication device of theconnection partner which has established the connection for a certainperiod. Such a technique is provided because, in a state where it isdetermined that the connection is disconnected as mentioned above, astate is considered where the physical wireless link cannot be secured,for example, the communication distance to the wireless communicationdevice of the connection destination is separated and the radio signalscannot be received or decoded. That is, it is because the reception ofthe frame to disconnect the connection cannot be expected.

As a specific example to determine the disconnection of connection in animplicit method, a timer is used. For example, at the time oftransmitting a data frame that requests an acknowledgment responseframe, a first timer (for example, a retransmission timer for a dataframe) that limits the retransmission period of the frame is activated,and, if the acknowledgement response frame to the frame is not receiveduntil the expiration of the first timer (that is, until a desiredretransmission period passes), retransmission is performed. When theacknowledgment response frame to the frame is received, the first timeris stopped.

On the other hand, when the acknowledgment response frame is notreceived and the first timer expires, for example, a management frame toconfirm whether a wireless communication device of a connection partneris still present (in a communication range) (in other words, whether awireless link is secured) is transmitted, and, at the same time, asecond timer (for example, a retransmission timer for the managementframe) to limit the retransmission period of the frame is activated.Similarly to the first timer, even in the second timer, retransmissionis performed if an acknowledgment response frame to the frame is notreceived until the second timer expires, and it is determined that theconnection is disconnected when the second timer expires.

Alternatively, a third timer is activated when a frame is received froma wireless communication device of the connection partner, the thirdtimer is stopped every time the frame is newly received from thewireless communication device of the connection partner, and it isactivated from the initial value again. When the third timer expires,similarly to the above, a management frame to confirm whether thewireless communication device of the connection party is still present(in a communication range) (in other words, whether a wireless link issecured) is transmitted, and, at the same time, a second timer (forexample, a retransmission timer for the management frame) to limit theretransmission period of the frame is activated. Even in this case,retransmission is performed if an acknowledgment response frame to theframe is not received until the second timer expires, and it isdetermined that the connection is disconnected when the second timerexpires. The latter management frame to confirm whether the wirelesscommunication device of the connection partner is still present maydiffer from the management frame in the former case. Moreover, regardingthe timer to limit the retransmission of the management frame in thelatter case, although the same one as that in the former case is used asthe second timer, a different timer may be used.

[3] Access Scheme of Wireless LAN System

For example, there is a wireless LAN system with an assumption ofcommunication or competition with a plurality of wireless communicationdevices. CSMA/CA is set as the basis of an access scheme in IEEE802.11(including an extension standard or the like) wireless LAN. In a schemein which transmission by a certain wireless communication device isgrasped and transmission is performed after a fixed time from thetransmission end, simultaneous transmission is performed in theplurality of wireless communication devices that grasp the transmissionby the wireless communication device, and, as a result, radio signalscollide and frame transmission fails. By grasping the transmission bythe certain wireless communication device and waiting for a random timefrom the transmission end, transmission by the plurality of wirelesscommunication devices that grasp the transmission by the wirelesscommunication device stochastically disperses. Therefore, if the numberof wireless communication devices in which the earliest time in a randomtime is subtracted is one, frame transmission by the wirelesscommunication device succeeds and it is possible to prevent framecollision. Since the acquisition of the transmission right based on therandom value becomes impartial between the plurality of wirelesscommunication devices, it can say that a scheme adopting CarrierAvoidance is a suitable scheme to share a radio medium between theplurality of wireless communication devices.

[4] Frame Interval of Wireless LAN

The frame interval of IEEE802.11 wireless LAN is described. There arevarious types of frame intervals used in IEEE802.11 wireless LAN, suchas distributed coordination function interframe space (DIFS),arbitration interframe space (AIFS), point coordination functioninterframe space (PIFS), short interframe space (SIFS), extendedinterframe space (EIFS) and reduced interframe space (RIFS).

The definition of the frame interval is defined as a continuous periodthat should confirm and open the carrier sensing idle beforetransmission in IEEE802.11 wireless LAN, and a strict period from aprevious frame is not discussed. Therefore, the definition is followedin the explanation of IEEE802.11 wireless LAN system. In IEEE802.11wireless LAN, a waiting time at the time of random access based onCSMA/CA is assumed to be the sum of a fixed time and a random time, andit can say that such a definition is made to clarify the fixed time.

DIFS and AIFS are frame intervals used when trying the frame exchangestart in a contention period that competes with other wirelesscommunication devices on the basis of CSMA/CA. DIFS is used in a casewhere priority according to the traffic type is not distinguished, AIFSis used in a case where priority by traffic identifier (TID) isprovided.

Since operation is similar between DIFS and AIFS, an explanation belowwill mainly use AIFS. In IEEE802.11 wireless LAN, access controlincluding the start of frame exchange in the MAC layer is performed. Inaddition, in a case where QoS (Quality of Service) is supported whendata is transferred from a higher layer, the traffic type is notifiedtogether with the data, and the data is classified for the priority atthe time of access on the basis of the traffic type. The class at thetime of this access is referred to as “access category (AC)”. Therefore,the value of AIFS is provided every access category.

PIFS denotes a frame interval to enable access which is morepreferential than other competing wireless communication devices, andthe period is shorter than the values of DIFS and AIFS. SIFS denotes aframe interval which can be used in a case where frame exchangecontinues in a burst manner at the time of transmission of a controlframe of a response system or after the access right is acquired once.EIFS denotes a frame interval caused when frame reception fails (whenthe received frame is determined to be error).

RIFS denotes a frame interval which can be used in a case where aplurality of frames are consecutively transmitted to the same wirelesscommunication device in a burst manner after the access right isacquired once, and a response frame from a wireless communication deviceof the transmission partner is not requested while RIFS is used.

Here, FIG. 19 illustrates one example of frame exchange in a competitiveperiod based on the random access in IEEE802.11 wireless LAN.

When a transmission request of a data frame (W_DATA1) is generated in acertain wireless communication device, a case is assumed where it isrecognized that a medium is busy (busy medium) as a result of carriersensing. In this case, AIFS of a fixed time is set from the time pointat which the carrier sensing becomes idle, and, when a random time(random backoff) is set afterward, data frame W_DATA1 is transmitted tothe communicating partner.

The random time is acquired by multiplying a slot time by a pseudorandominteger led from uniform distribution between contention windows (CW)given by integers from 0. Here, what multiplies CW by the slot time isreferred to as “CW time width”. The initial value of CW is given byCWmin, and the value of CW is increased up to CWmax everyretransmission. Similarly to AIFS, both CWmin and CWmax have valuesevery access category. In a wireless communication device oftransmission destination of W_DATA1, when reception of the data framesucceeds, a response frame (W_ACK1) is transmitted after SIFS from thereception end time point. If it is within a transmission burst timelimit when W_ACK1 is received, the wireless communication device thattransmits W_DATA1 can transmit the next frame (for example, W_DATA2)after SIFS.

Although AIFS, DIFS, PIFS and EIFS are functions between SIFS and theslot-time, SIFS and the slot time are defined every physical layer.Moreover, although parameters whose values being set according to eachaccess category, such as AIFS, CWmin and CWmax, can be set independentlyby a communication group (which is a basic service set (BSS) inIEEE802.11 wireless LAN), the default values are defined.

For example, in the definition of 802.11ac, with an assumption that SIFSis 16 μs and the slot time is 9 μs, and thereby PIFS is 25 pis, DIFS is34 μs, the default value of the frame interval of an access category ofBACKGROUND (AC_BK) in AIFS is 79 μs, the default value of the frameinterval of BEST EFFORT (AC_BE) is 43 μs, the default value of the frameinterval between VIDEO(AC_VI) and VOICE(AC_VO) is 34 μs, and the defaultvalues of CWmin and CWmax are 31 and 1023 in AC_BK and AC_BE, 15 and 31in AC_VI and 7 and 15 in AC_VO. Here, EIFS denotes the sum of SIFS,DIFS, and the time length of a response frame transmitted at the lowestmandatory physical rate. In the wireless communication device which caneffectively takes EIFS, it may estimate an occupation time length of aPHY packet conveying a response frame directed to a PHY packet due towhich the EIFS is caused and calculates a sum of SIFS, DIFS and theestimated time to take the EIFS.

The terms used in each embodiment should be interpreted broadly. Forexample, the term “processor” may encompass a general purpose processor,a central processing unit (CPU), a microprocessor, a digital signalprocessor (DSP), a controller, a microcontroller, a state machine, andso on. According to circumstances, a “processor” may refer to anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA), and a programmable logic device (PLD), etc. The term“processor” may refer to a combination of processing devices such as aplurality of microprocessors, a combination of a DSP and amicroprocessor, or one or more microprocessors in conjunction with a DSPcore.

As another example, the term “memory” may encompass any electroniccomponent which can store electronic information. The “memory” may referto various types of media such as a random access memory (RAM), aread-only memory (ROM), a programmable read-only memory (PROM), anerasable programmable read only memory (EPROM), an electrically erasablePROM (EEPROM), a non-volatile random access memory (NVRAM), a flashmemory, and a magnetic or optical data storage, which are readable by aprocessor. It can be said that the memory electronically communicateswith a processor if the processor read and/or write information for thememory. The memory may be arranged within a processor and also in thiscase, it can be said that the memory electronically communication withthe processor. The term “circuitry” may refer to not only electriccircuits or a system of circuits used in a device but also a singleelectric circuit or a part of the single electric circuit. Moreover, theterm “circuitry” may refer one or more electric circuits disposed on asingle chip, or may refer one or more electric circuits disposed on aplurality of chips more than one chip or a plurality of devices in adispersed manner.

In the specification, the expression “at least one of a, b or c” is anexpression to encompass not only “a”, “b”, “c”, “a and b”, “a and c”, “band c”, “a, b and c” or any combination thereof but also a combinationof at least a plurality of same elements such as “a and a”, “a, b and b”or “a, a, b, b, c and c”. Also, the expression is an expression to allowa set including an element other than “a”, “b” and “c” such as “a, b, c,and d”.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions.

1. A wireless communication device comprising: a memory configured tostore a plurality of radiation pattern selection policies on an antennacapable of changing a radiation pattern; and processing circuitryconfigured to detect an interference signal of a first channel byanalyzing a signal received via the antenna; and select the radiationpattern selection policy from among the plurality of radiation patternselection policies based on the interference signal of the first channeland change the radiation pattern of the antenna in accordance with theselected radiation pattern selection policy.
 2. The wirelesscommunication device according to claim 1, wherein the processingcircuitry is configured to judge whether an occurrence source of theinterference signal is a device belonging to a predetermined category byanalyzing the received signal; and the processing circuitry isconfigured to select a first policy from among the plurality ofradiation pattern selection policies when judging that the occurrencesource is a device belonging to the predetermined category and select asecond policy different from the first policy when judging that theoccurrence source is not a device belonging to the predeterminedcategory.
 3. The wireless communication device according to claim 1,wherein the processing circuitry is configured to judge whether a ratioof a period during which the interference signal is detected within afirst period is equal to or above a predetermined value, select a firstpolicy from among the plurality of radiation pattern selection policieswhen the ratio is equal to or above the predetermined value and select asecond policy different from the first policy when the ratio is belowthe predetermined value.
 4. The wireless communication device accordingto claim 2, wherein the first policy prescribes that a radiation patternis to be randomly selected from among a plurality of radiation patterns.5. The wireless communication device according to claim 2, wherein thefirst policy prescribes that a radiation pattern having directivity in adirection toward an interference source in the first channel is to beselected.
 6. The wireless communication device according to claim 2,wherein the second policy prescribes that a radiation pattern is to beselected based on a history of communication performed in each of theplurality of radiation patterns.
 7. The wireless communication deviceaccording to claim 2, wherein the second policy prescribes thatcommunication quality of each of the plurality of radiation patterns isto be measured and a radiation pattern is to be selected according tothe measured communication quality.
 8. The wireless communication deviceaccording to claim 2, wherein the processing circuitry is configured tocontrol communication in accordance with a communication scheme in whichcarrier sensing on a wireless medium is performed and when the state ofthe wireless medium is idle, transmission is allowed; and the processingcircuitry is configured to increase a threshold for reception judgmentin the carrier sensing when the first policy is selected.
 9. Thewireless communication device according to claim 1, comprising acommunicator configured to transmit first information notifying that thefirst channel is to be switched to a second channel, via the firstchannel after the radiation pattern of the antenna is changed.
 10. Thewireless communication device according to claim 9, wherein theprocessing circuitry is configured to switch the first channel to thesecond channel after the first information is transmitted.
 11. Thewireless communication device according to claim 1, comprising theantenna.
 12. A wireless communication terminal comprising: at least oneantenna capable of changing a radiation pattern; a receiver coupled withthe antenna and configured to receive a frame; a transmitter coupledwith the antenna and configured to transmit a frame; a communicationprocessor coupled with the receiver and the transmitter; a networkprocessor coupled with the communication processor and configured totransmit data to the communication processor and receive data from otherdevices; and a memory coupled with the network processor and configuredto cache first data; wherein the communication processor is configuredto detect an interference signal of a first channel by analyzing asignal received via the antenna, decide a radiation pattern selectionpolicy based on the interference of the first channel, and change theradiation pattern of the antenna in accordance with the radiationpattern selection policy; the transmitter is configured to transmit afirst frame via the antenna with the changed radiation pattern; and thefirst frame includes the first data cached in the memory or informationbased on the first data.
 13. A wireless communication method comprising:detecting an interference signal of a first channel by analyzing asignal received via an antenna capable of changing a radiation pattern;and deciding a radiation pattern selection policy based on theinterference signal of the first channel; change the radiation patternof the antenna in accordance with the radiation pattern selectionpolicy.
 14. The method according to claim 13, further comprising judgingwhether an occurrence source of the interference signal is a devicebelonging to a predetermined category by analyzing the received signal;and selecting a first policy from among a plurality of radiation patternselection policies when judging that the occurrence source is a devicebelonging to the predetermined category and selecting a second policydifferent from the first policy when judging that the occurrence sourceis not a device belonging to the predetermined category.
 15. The methodaccording to claim 13, further comprising judging whether a ratio of aperiod during which the interference signal is detected within a firstperiod is equal to or above a predetermined value, selects a firstpolicy from among a plurality of radiation pattern selection policieswhen the ratio is equal to or above the predetermined value andselecting a second policy different from the first policy when the ratiois below the predetermined value.
 16. The method according to claim 14,wherein the first policy prescribes that a radiation pattern is to berandomly selected from among a plurality of radiation patterns.
 17. Themethod according to claim 14, wherein the first policy prescribes that aradiation pattern having directivity in a direction toward aninterference source in the first channel is to be selected.
 18. Themethod according to claim 14, wherein the second policy prescribes thata radiation pattern is to be selected based on a history ofcommunication performed in each of the plurality of radiation patterns.19. The method according to claim 14, wherein the second policyprescribes that communication quality of each of the plurality ofradiation patterns is to be measured, and a radiation pattern is to beselected according to the measured communication quality.
 20. The methodaccording to claim 14, further comprising controlling communication inaccordance with a communication scheme in which carrier sensing on awireless medium is performed and when the state of the wireless mediumis idle, transmission is allowed; and increasing a threshold forreception judgment in the carrier sensing when the first policy isselected.